Johnson 2004 - CDLI - UCLA

The sentence in (6a) does not have (6b) as its presupposition; instead, it has the original,
non-negative version of (6b) as its presupposition, namely (1b): “She has a husband.”
Basically, a presupposition remains true even when the sentence in which it occurs is
negated. Unlike the example of a negated entailment in (5b), however, the negation of the
presupposition as in (6b) does not so much result in a negative sentence such as (6a) as
the feeling that the assertion in (6a) no longer makes any sense in the first place; the
negation of presuppositions has recently been discussed by Herburger (2000) under the
heading of “backgrounded focal entailment” and we return to her discussion of the matter
briefly in the following section (for a case-study in the use of negation to pick apart
presupposition and entailment in an archaeologically recovered language like Sumerian,
see Loprieno 1991).
If someone asserts that something is the case in a particular sentence, however, the
part of the sentence that is being asserted will not, as a rule, be part of the presupposition:
clearly one cannot presuppose and assert the same thing at the same time. In (1a), for
example, the part of the sentence that the speaker is asserting is that someone is a fool,
whereas the part of a sentence that is being presupposed is that there is someone who
meets the criterion of being her husband. In English, this contrast is particularly evident
in existential sentences with there in “subject” position as in (8) because the usual
location of presuppositional elements is in the subject position, here occupied by “there.”
(7) There is a rat in your soup.
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